In the dispensing field, it is common to mix two or more viscous fluid components to form a mixed fluid shortly before dispensing. For example, first and second viscous fluids, such as first and second liquid adhesive components, may be mixed to form a curable liquid adhesive for application onto a workpiece or substrate. The fluids may be initially contained in separate cartridges and directed under slight pressure to respective first and second fluid passageways. A metering rod in each passageway may be used to force or direct the first and second fluids from the first and second fluid passageways and into a mixing passage. The mixing passage will contain a static mixer in a nozzle. Accordingly, the first and second viscous fluids travel through the static mixer within the nozzle to dispense from a dispensing passageway at the nozzle tip for application onto the workpiece or substrate. While this particular example forms a curable liquid adhesive for dispensing, a number of fluid components may be similarly mixed to create a mixed fluid that includes any variety of desirable properties for use by the end-user.
Various challenges arise when attempting to dispense very small or minute beads of materials. For example, these minute beads of material may have a diameter of between about 0.2 mm and about 0.4 mm and a total volume of about 0.02 cc or more. When dispensing such small volumes of these viscous materials, in an application requiring high degrees of accuracy, the need for clean cutoff at the end of the dispensing cycle for a given bead is paramount as is the need to prevent any undesirable volume changes in the dispensed amount as the dispensed cycle ends.